Smoke Testing: A Detailed Guide

Smoke testing is a method of verifying the basic functionality of an application to decide if other more advanced features should be tested.

In this article, we’ll explore the essentials of smoke testing: what it is, how it works, and why it’s a critical step in delivering reliable software.

What is Smoke Testing?

Smoke testing is the process of testing the most basic features of an application. If the application passes the smoke test, it is stable enough for more in-depth testing; otherwise, it is sent back to the development team for a fix.

Why Smoke Testing?

Think of smoke testing as doing a quick simple math equation on a calculator. If you key in 1 + 1 and the calculator returns a result of 3, you probably won’t continue to use it to solve a quadratic function. Smoke testing is a quick screening for the overall health of your system before any deep-diving.

Smoke testing is quick, it’s focused, and it’s your first line of defense against releasing a broken build. It is often automated due to the simple and repetitive nature.

Fun fact: the term "smoke testing" actually originates from hardware testing. In the early days of hardware development, engineers would power up a device or circuit for the first time and check for literal smoke, which usually means a short circuit (or serious problem in general). If no smoke appeared, it was a sign that the hardware could proceed to more detailed and thorough testing.

This concept was later adapted to software development. In software, "smoke testing" metaphorically checks whether the application "catches fire" when its core functionalities are tested.

Characteristics of Smoke Testing

1. Early Stability Check: smoke testing is done early on a new software build. The goal is to check its stability before advanced testing.

2. Core Focus: it focuses solely on key features to ensure the build's basic operability.

3. Fast Execution: it is a short and sweet check for rapid feedback.

Smoke Testing vs. Sanity Testing

A relatively similar type of testing is sanity testing.

Sanity testing checks that specific features work as expected after a code change. Its scope is much more focused than smoke testing.

Here is a quick comparison between them:

Smoke Testing Process

Smoke testing doesn’t have to be complicated—it’s all about being quick and effective. Here’s how you can do it step by step: 

1. Pinpoint the Essentials
   Start by identifying the most critical features of your application—the ones that must work for anything else to matter. Think login functionality, navigation, or core operations like placing an order.
2. Write Simple Test Cases
   Create straightforward test cases that target these key features. Keep it light and focused; this isn’t the time to dive into edge cases or complex scenarios.
3. Run and Review
   Execute your tests. If something fails, note it down, and stop. No point in testing further if the basics aren’t working. Analyze results to understand whether the application is stable enough to proceed.
4. Automate for Speed
   Save time and effort by automating smoke tests for future builds. Tools like Katalon Studio or Selenium make it easy to set up automated tests that run with every new build.

Smoke Testing Best Practices

To get the most out of smoke testing, keep these best practices in mind:

1. Focus on the Essentials
   Don’t overcomplicate it—stick to testing the most critical functionality. These are the features that ensure the application can run at all.
2. Keep Tests Simple
   Smoke tests aren’t about digging deep; they’re about speed and clarity. Use straightforward test cases to quickly identify blockers without spending too much time on details.
3. Automate When Possible
   Manual smoke testing is fine for small projects, but automation is a game-changer. 
4. Integrate with CI/CD
   Incorporate smoke tests into your CI/CD pipeline. This ensures every new build is checked for stability before progressing to deeper testing phases.